The present invention is related to large capacitors with arrays, or parallel banks, of multilayered ceramic capacitors (MLCC's). More specifically, the present invention is related to very large arrays of MLCC's on a flexible support, preferably in electrical parallel, with protection from mechanical stresses.
MLCC's are typically produced in relatively small case sizes as discrete components. Other capacitor technologies, such as film capacitors, can be formed as large devices and wound or stacked to produce large bricks. Similarly, electrolytic type capacitors can be made using large cans or housings. Unfortunately, film and electrolytic capacitors perform poorly in some environments such as at elevated temperatures which limits their use.
MLCC's exhibit some desirable properties such as the ability to withstand higher temperature however, in order to realize these benefits the smaller MLCC's have to be stacked into large rigid arrays to achieve the higher capacitance needed for many applications. This stacking is usually achieved by soldering or bonding the terminals of a stack of MLCC's to a lead frame. The subsequent stack is then attached to the circuit of the final device to form electrical and mechanical contacts. These lead frames offer some additional robustness with respect to resisting an external bending force applied to the device during assembly or application and with respect to coefficient of thermal expansion mismatch on temperature cycling. Unfortunately, the large mass of the leaded stack causes the stack to be more prone to failures caused by mechanical shock. If the final assembled device is dropped the energy can be transferred through the attached lead frame causing cracks in the ceramic, or attachments, which leads to electrical failure.
Those of skill in the art have been limited to the use of either a large capacitor, with film or electrolytic technologies, which are incapable of withstanding adverse environmental conditions, or stacks of MLCC's attached to leads which are unsuitable for harsh mechanical conditions. There has been a continuous need in the art for a capacitor which can withstand both environmental deviations from normal and mechanical shock. This need has not been previously met.
Provided herein is a large packaged array of ceramic based capacitors with improved resilience to subsequent mechanical shocks. This is achieved by assembling MLCC's into large capacitor banks, or arrays, using flexible substrates that can then subsequently be assembled within a low volume package for attachment to the final device.